/* ============================================================
   「学到爽」PC 介绍页样式
   品牌色：#667eea（与微信小程序导航栏一致）
   北京立形科技有限公司
   ============================================================ */

/* ---------- 基础变量 ---------- */
:root {
  --brand: #667eea;
  --brand-dark: #5a67d8;
  --brand-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --text-main: #2d3748;
  --text-sub: #718096;
  --bg-main: #ffffff;
  --bg-alt: #f7f8fc;
  --border: #eef0f6;
  --radius: 16px;
  --shadow: 0 12px 32px rgba(102, 126, 234, 0.12);
  --shadow-lg: 0 24px 56px rgba(45, 55, 72, 0.16);
  --container-w: 1180px;
}

/* ---------- 基础重置 ---------- */
* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei",
    "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--text-main);
  background: var(--bg-main);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: var(--container-w);
  margin: 0 auto;
  padding: 0 24px;
}

a { color: inherit; text-decoration: none; }

/* ---------- 顶部导航栏 ---------- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: transparent;
  transition: background 0.3s ease, box-shadow 0.3s ease, backdrop-filter 0.3s ease;
}
/* 滚动后导航栏背景 */
.site-header.scrolled {
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  box-shadow: 0 2px 16px rgba(45, 55, 72, 0.08);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 700;
  color: #fff;
}
.site-header.scrolled .nav-brand { color: var(--text-main); }

.brand-logo {
  width: 40px;
  height: 40px;
  border-radius: 10px;
  /* logo 为白底满幅图（含四周黑色描边），必须 contain 完整展示，禁止 cover 裁切 */
  object-fit: contain;
  flex-shrink: 0;
  background: #fff;
  vertical-align: middle;
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}
.brand-logo-lg { width: 72px; height: 72px; border-radius: 16px; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}
.nav-link {
  color: #fff;
  font-size: 15px;
  opacity: 0.9;
  transition: opacity 0.2s ease;
  position: relative;
}
.site-header.scrolled .nav-link { color: var(--text-main); }
.nav-link:hover { opacity: 1; }
.nav-link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -6px;
  width: 0;
  height: 2px;
  background: var(--brand);
  transition: width 0.25s ease;
}
.nav-link:hover::after { width: 100%; }

/* 移动端菜单按钮 */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 6px;
}
.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  border-radius: 2px;
  background: #fff;
  transition: transform 0.3s ease, opacity 0.3s ease;
}
.site-header.scrolled .nav-toggle span { background: var(--text-main); }
.nav-toggle.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.open span:nth-child(2) { opacity: 0; }
.nav-toggle.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ---------- Hero 首屏区 ---------- */
.hero {
  position: relative;
  background: var(--brand-gradient);
  color: #fff;
  overflow: hidden;
  padding: 140px 0 120px;
}
.hero::before {
  content: "";
  position: absolute;
  top: -40%;
  right: -10%;
  width: 600px;
  height: 600px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.06);
}
.hero::after {
  content: "";
  position: absolute;
  bottom: -30%;
  left: -8%;
  width: 480px;
  height: 480px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.05);
}

.hero-inner {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 48px;
  align-items: center;
}

.hero-tag {
  display: inline-block;
  font-size: 13px;
  letter-spacing: 1px;
  background: rgba(255, 255, 255, 0.16);
  border: 1px solid rgba(255, 255, 255, 0.24);
  padding: 6px 14px;
  border-radius: 999px;
  margin-bottom: 24px;
}

.hero-title {
  font-size: 52px;
  font-weight: 800;
  line-height: 1.25;
  letter-spacing: 1px;
  margin-bottom: 20px;
}
.hero-title b { color: #ffd76e; }

.hero-subtitle {
  font-size: 17px;
  line-height: 1.9;
  opacity: 0.94;
  max-width: 560px;
  margin-bottom: 32px;
}

.hero-actions {
  display: flex;
  gap: 16px;
  margin-bottom: 36px;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 13px 30px;
  border-radius: 999px;
  font-size: 15px;
  font-weight: 600;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}
.btn:hover { transform: translateY(-2px); }

.btn-primary {
  background: #fff;
  color: var(--brand-dark);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.18);
}
.btn-primary:hover { box-shadow: 0 12px 32px rgba(0, 0, 0, 0.24); }

.btn-ghost {
  border: 1.5px solid rgba(255, 255, 255, 0.6);
  color: #fff;
}
.btn-ghost:hover { border-color: #fff; background: rgba(255, 255, 255, 0.1); }

.hero-points {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 12px 28px;
  font-size: 14px;
  opacity: 0.92;
}

/* Hero 设备图 */
.hero-visual { position: relative; display: flex; justify-content: center; }

.device {
  width: 260px;
  padding: 12px;
  border-radius: 34px;
  background: #1f2430;
  box-shadow: var(--shadow-lg);
  transform: perspective(1200px) rotateY(-8deg) rotateX(2deg);
  transition: transform 0.4s ease;
}
.device:hover { transform: perspective(1200px) rotateY(-4deg) rotateX(1deg); }

.device-screen {
  border-radius: 24px;
  overflow: hidden;
  background: #f5f7fb;
}
/* 小程序真实界面截图（模拟器 389x836 竖屏），等比缩放完整显示 */
.device-shot {
  display: block;
  width: 100%;
  height: auto;
}

/* 浮动装饰标签 */
.hero-float {
  position: absolute;
  background: #fff;
  color: var(--text-main);
  font-size: 13px;
  font-weight: 600;
  padding: 9px 16px;
  border-radius: 999px;
  box-shadow: var(--shadow);
  animation: floatY 3.2s ease-in-out infinite;
}
.hero-float.float-1 { top: 12%; left: -6%; }
.hero-float.float-2 { bottom: 20%; right: -4%; animation-delay: 0.6s; }
.hero-float.float-3 { top: 46%; left: -12%; animation-delay: 1.2s; }

@keyframes floatY {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

/* Hero 底部波浪 */
.hero-wave {
  position: absolute;
  bottom: -2px;
  left: 0;
  right: 0;
  height: 80px;
  background: var(--bg-main);
  border-radius: 50% 50% 0 0 / 32% 32% 0 0;
}

/* ---------- 通用 Section ---------- */
.section { padding: 96px 0; }
.section-alt { background: var(--bg-alt); }
.section-brand {
  background: var(--brand-gradient);
  color: #fff;
}

.section-head {
  text-align: center;
  max-width: 640px;
  margin: 0 auto 56px;
}

.section-tag {
  display: inline-block;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 2px;
  color: var(--brand);
  background: rgba(102, 126, 234, 0.1);
  padding: 6px 16px;
  border-radius: 999px;
  margin-bottom: 16px;
}
.section-tag-light { color: #fff; background: rgba(255, 255, 255, 0.16); }

.section-title {
  font-size: 34px;
  font-weight: 800;
  letter-spacing: 0.5px;
  margin-bottom: 14px;
}
.section-title-light { color: #fff; }

.section-desc { font-size: 16px; color: var(--text-sub); }
.section-brand .section-desc { color: rgba(255, 255, 255, 0.86); }

/* ---------- 卡片网格 ---------- */
.cards-grid {
  display: grid;
  gap: 24px;
}
.cards-3 { grid-template-columns: repeat(3, 1fr); }
.cards-4 { grid-template-columns: repeat(4, 1fr); }

.card {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 26px;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow);
}

.card-icon {
  font-size: 40px;
  line-height: 1;
  margin-bottom: 18px;
}

.card h3 { font-size: 19px; font-weight: 700; margin-bottom: 10px; }
.card p { font-size: 14.5px; color: var(--text-sub); }

.feature-list {
  list-style: none;
  margin-top: 16px;
  padding-top: 16px;
  border-top: 1px dashed var(--border);
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-size: 13px;
  color: var(--text-sub);
}
.feature-list li { position: relative; padding-left: 18px; }
.feature-list li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--brand);
  font-weight: 700;
}

/* ---------- 三步走流程 ---------- */
.flow-steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  position: relative;
}
/* 步骤间连接线 */
.flow-steps::before {
  content: "";
  position: absolute;
  top: 40px;
  left: 16.6%;
  right: 16.6%;
  height: 2px;
  background: linear-gradient(90deg, var(--brand), var(--brand) 100%);
  opacity: 0.18;
  z-index: 0;
}

.flow-step {
  position: relative;
  z-index: 1;
  display: flex;
  gap: 18px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 26px;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.flow-step:hover { transform: translateY(-6px); box-shadow: var(--shadow); }

.flow-num {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 52px;
  height: 52px;
  flex-shrink: 0;
  border-radius: 50%;
  background: var(--brand-gradient);
  color: #fff;
  font-size: 22px;
  font-weight: 800;
  box-shadow: 0 8px 20px rgba(102, 126, 234, 0.35);
}

.flow-body h3 { font-size: 19px; font-weight: 700; margin-bottom: 8px; }
.flow-body p { font-size: 14.5px; color: var(--text-sub); }
.flow-demo {
  display: inline-block;
  margin-top: 12px;
  font-size: 12.5px;
  color: var(--brand-dark);
  background: rgba(102, 126, 234, 0.08);
  padding: 4px 12px;
  border-radius: 999px;
}

/* ---------- 技术架构 ---------- */
.tech-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

.tech-item {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 22px;
  text-align: center;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.tech-item:hover { transform: translateY(-6px); box-shadow: var(--shadow); }

.tech-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 30px;
  border-radius: 18px;
  background: rgba(102, 126, 234, 0.1);
}

.tech-item h3 { font-size: 16.5px; font-weight: 700; margin-bottom: 8px; }
.tech-item p { font-size: 13.5px; color: var(--text-sub); line-height: 1.75; }

.tech-note {
  margin-top: 32px;
  text-align: center;
  font-size: 14px;
  color: var(--text-sub);
  background: rgba(102, 126, 234, 0.07);
  border: 1px dashed rgba(102, 126, 234, 0.35);
  border-radius: 12px;
  padding: 14px 20px;
}

/* ---------- 公司介绍 ---------- */
.about-inner {
  display: grid;
  grid-template-columns: 0.7fr 1.3fr;
  gap: 48px;
  align-items: center;
}

.about-logo {
  display: flex;
  justify-content: center;
}
.about-logo .brand-logo-lg { box-shadow: 0 12px 32px rgba(0, 0, 0, 0.22); }

.about-content .section-tag-light { margin-top: 0; }
.about-content p {
  font-size: 15.5px;
  line-height: 2;
  color: rgba(255, 255, 255, 0.92);
  margin-bottom: 14px;
}

/* ---------- 页脚 ---------- */
.site-footer {
  background: #1f2430;
  color: #aeb6c4;
  padding-top: 64px;
}

.footer-inner {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr 1fr;
  gap: 32px;
  padding-bottom: 40px;
}

.footer-brand .brand-logo { box-shadow: 0 6px 16px rgba(0, 0, 0, 0.35); }
.footer-brand .brand-name {
  color: #fff;
  font-size: 18px;
  font-weight: 700;
  vertical-align: middle;
  margin-left: 8px;
}
.footer-brand p { margin-top: 12px; font-size: 14px; }

.footer-col h4 {
  color: #fff;
  font-size: 15px;
  font-weight: 600;
  margin-bottom: 16px;
}
.footer-col a,
.footer-col span {
  display: block;
  font-size: 14px;
  margin-bottom: 10px;
  opacity: 0.85;
  transition: opacity 0.2s ease;
}
.footer-col a:hover { opacity: 1; color: var(--brand); }

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  text-align: center;
  padding: 20px 0;
  font-size: 13px;
  opacity: 0.7;
}
/* 备案号链接（工信部备案查询） */
.footer-bottom .beian-link {
  color: #aeb6c4;
  transition: opacity 0.2s ease, color 0.2s ease;
}
.footer-bottom .beian-link:hover {
  color: var(--brand);
  opacity: 1;
}

/* ---------- 滚动渐显动画 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---------- 响应式适配 ---------- */
@media (max-width: 1024px) {
  .cards-4, .tech-grid { grid-template-columns: repeat(2, 1fr); }
  .hero-title { font-size: 42px; }
  .hero-inner { grid-template-columns: 1fr; gap: 56px; }
  .hero-visual { order: -1; }
  .hero-float.float-1 { left: 4%; }
  .hero-float.float-2 { right: 4%; }
  .hero-float.float-3 { left: 8%; }
}

@media (max-width: 768px) {
  .section { padding: 64px 0; }
  .cards-3, .cards-4, .tech-grid, .flow-steps { grid-template-columns: 1fr; }
  .flow-steps::before { display: none; }
  .about-inner { grid-template-columns: 1fr; gap: 32px; }
  .footer-inner { grid-template-columns: 1fr 1fr; }

  /* 移动端导航 */
  .nav-toggle { display: flex; }
  .nav-links {
    position: fixed;
    top: 72px;
    right: 0;
    flex-direction: column;
    align-items: flex-start;
    gap: 4px;
    background: #fff;
    padding: 16px 24px;
    border-radius: 0 0 0 16px;
    box-shadow: var(--shadow);
    transform: translateX(100%);
    transition: transform 0.3s ease;
  }
  .nav-links.open { transform: translateX(0); }
  .nav-link { color: var(--text-main); padding: 8px 0; width: 100%; }

  .hero-title { font-size: 34px; }
  .hero { padding: 120px 0 90px; }
}

@media (max-width: 480px) {
  .hero-title { font-size: 30px; }
  .btn { padding: 12px 22px; font-size: 14px; }
}